Method of preparing petroleum wax compositions containing a small amount of a polyethylene



Patented May 12, 1953 METHOD OF PREPARING PETROLEUM WAX COMPOSITIONS CONTAINING A SMALL AMOUNT OF A POLYETHYLENE John R. Bowman and William P. Ridenour, Pittsburgh, Pa., and June Hollenback Whittaker, Lombard, Ill., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Application December 4, 1950, Serial No. 199,154

9 Claims- (Cl. 26028.5)

This invention relates to improved petroleum wax compositions, and more particularly it relates to stable homogeneous high tensile strength paraffin Wax compositions containing high molecular weight ethylene polymers and the method of preparing such-waxcompositiona This application is a continuation-in-part of our prior copending application Serial No.

601,556, filed June 25, 1945, and assigned to the same assignee as the instant application.

In many of the applications of paraffin wax in industry, improved tensile strength is a desirable factor. For example, in the case of socalled paper milk bottles, which are paper bottles coated with paraflin wax, the tensile strength of the wax is particularly important because of the strain to which the bottle is subjected in handling.

In any composition of paraffin wax designed to increase tensile strength other inherently desirable features of the paraffin wax should no be reduced.

It should, for example, not block (tendency for a pile or roll of waxed paper to adhere together). entrained air) and a tendency toward scufling found particularly in parafiln wax are undesirable and it is desired to reduce such tendencies.

The use of high molecular weight ethylene polymers in admixture with paraffin waxes, particularly for the. coating or waxingof paper and the like has not been practical because the high molecular weight solid ethylene polymers dissolve with difilculty in molten parafiin wax even at temperatures at 150 F.-160 F., normally used for waxing machine operations. While the solid ethylene polymers in melted condition are miscible with paraffins in all proportions, they tend to crystallize from solution at temperatures below about 230 F.

It is therefore an object of this invention to produce a petroleum wax composition of increased tensile strength.

It is a further object of this invention to produce a paraflin wax composition of increased tensile strength Without decreasing other desirable features of paraffin wax. I

It is a further object of this invention to produce a composition of parafiin wax of increased tensile strength with decreased mottling and scufiing characteristics.

' It is also an object of the present invention to provide stable ,homogeneous wax compositions containing high molecular weight ethylene polymers. Another object of the invention is tOPI'O-u Mottling (a disfiguration caused by 'vide a high tensile strength, stable, homogeneous paraffin wax composition containing high molecular weight ethylene polymers suitable for waxing paper.

Another object of the invention is to provide a method of rapidly bringing a high molecular weight ethylene polymer in solution in a petroleum wax.

Other objects and advantages of the invention will become apparent from the following description thereof.

We have discovered that petroleum wax compositions containing high molecular weight ethylene polymers, which possess high tensile strength properties and which remain homogenous, can be obtained by incorporating in the wax small but suflicient amounts of solid ethylene polymers to substantially increase the tensile strength of the wax but insuificient to have a substantial efiect upon other desirable properties of the wax. For example, we have found that these properties can be attained by incorporating in the wax'from about 0.001% to about 0.2% (by weight) of ethylenepolymers having average molecular weights of from about 5,000

to about 25,000, and preferably from about 10,000 to about 20,000. For certain uses Where a slight haze or cloud is not objectionable, we can use up to 1.0%, or even up to 7%, of the ethylene polymer. In its broader aspects, then, our invention contemplates a petroleum wax "composition containingan amount of solid polymerized ethylene suflicient to increase tensile strength but not substantially to change other desirable characteristics of the petroleum wax,

and usually from about 0.001 to about 7 per cent of the total composition. Good results are obtained with from about 0.1 to about 0.5 per cent of solid polymerized ethylene.

The high molecular weight solid ethylene polymers can be obtained by subjecting ethylene to pressures above 500 atmospheres and temperatures above about 100 C. The high pressure and temperature method of preparing-high molecular weight ethylene polymers is described in detail in U. S. 2,153,553 issued to E. W. Fawcett et al. April 11, 1939. Another method of preparing high molecular weight ethylene polymers is described in U. S; 2,188,465 issued to M. W.

Perrin et al. January 30, 1940. The polymerized ethylene can have a molecular weight as high as 80,000 or more. One type which has been found highly desirable is known as Polythene and has an average molecular weight in the range of 18,000 to 20,000, :a specific gravity; of

one polymer, respectively. dissolved in the molten wax,the temperature insure homogeneity.

12 inches per minute. :measured in pounds per' A square inch and was determined for each :blend and the uncom- 3 0.92 and a softening temperature (transparency point) of 105 C.

The petroleum wax used can be a crystalline or parafin wax or a .microcrystalline or amor- 4 pounded wax by averaging the tensile strengths found for the five individual test briquettes of ch composition. The .tensile strengths are shown in Table I.

TABLE I Concentration of Polymerized Ethylene, Pore cent 0.25 0.5 1.0 2.0 3.0 5.0 Average Tensile Strength,

Lbs/$4 sq. in 95. 97 1.27. 6 I 135. 58 143. 41 144. 32 140. 27 157. 3

phone wax such as a petrolatum wax having melting points of from about 140 F. to about 180 F. and preferably from about 145 Flto about 165 F. The petroleum waxes best adapted for use in the present invention are the crys-.

talline or paraihn waxes having melting points (If-from about 120 F. to about 140 and preferably from about 130 Rte about 135 such waxes are used for the coating or waxing of paper. Preferably the wax should not have an oil content greater than 0.5 per cent.

The high molecular weight ethylene polymers are dissolved with difficulty'in molten petroleum waxes. However, the solution of such polymers in molten waxes can be greatly facilitated and accelerated by first forming a blend of the polymer containing from about 5% to about 6 0% of the wax, preferably by milling at a temperature of from about 220 F. to about 360 F., and then dissolving the polymer-wax blend in the wax at a temperature of about 140 F. to about 250 F. The blend of ethylene polymer and wax can be prepared by stabilizing the ethylene polymer with a small amount of a stabilizer or anti-- oxidant and milling the paraffin wax into the polymer at about 270 F. Although'the milled blend becomes opaque on cooling the mixture remains very intimate or homogeneous.

The following examples are illustrative of the present invention.

Example 1.In" order to dissolve polymerized ethylene in parafiin wax, an ethylene polymer having an average molecular weight of about 18,000 to 20,000 was mixed with an equal weight of a 132 (ASTM) melting point paraflin wax and the mixture was maintained at329 F. until it became fluid enough to flow freely. The blend was then poured into successive portions of molten paraffin wax (132 F. melting point) in amounts sufiicient to result in the final paraffin wax-ethylene polymer compositions containing 0.25, 0.5, 1, 2, 3 and 5%'by weight of ethy The blend readily of the mixtures beingmaintained at 212 F. to Upon cooling to the solid state, the final compositions were homogeneous and were not mottled. Small percentages of the polymerized ethylene gave large increases in tensile strength.

Thetensile strengths of the blends and of the uncompounded wax were determined by the Perkins test, described in Bureau of Mines Bul- "letin No. 388, by R. H. Espach. Five test briquettes were prepared for each blend by pouring the blends into the briquette molds at 100- 110 C. and then aging them at 70 F. for hours. The rate of pull on the test machine was The tensile strength was EwampZe-ls-Equ-al quantities of paraffin wax havinga melting point of 132 F. (ASTM) and polymerized ethylene were warmed under conditions avoiding superheating to a temperature of about 329 F. with stirring. This treatment ,merized ethylene.

sealing characteristics.

was continued for about an hour and the product was then mixed withqa further quantity of the same paraifin wax in a molten state such that thetotal composition contained 10.5% beli The final product was .determined to have a tensile strength of pounds by the Perkins test as compared with '93 pounds for the parafiin wax alone.

Example 3.--P-olymerized ethylene was blended with a 132 F. meltin pOint para fin wax and a 122 F. melting point parafiin wax respectively by the procedure of Example 1. For each wax, there were prepared three blends containing re- ..spectively, 0.01, 0.05 and 0.1 per cent weight of ethylene polymer. the blends and of the uncompounded waxes is shown in Table II.

The tensile strength or Example -4.-A blend of a microcrystalline or amorphous petroleum wax (Gilli- Petrowax A) containing 1 per cent by weight of polymerized ethylene was prepared by the procedure of Example 1.

When the ten-side strengths of the blend and uncompounded petroleum wax were determined by the Perkins test, it was found that the blend had a tensile strength of 52 pounds, whereas the uncompounded wax had a tensile strength of 45 pounds.

In addition to having improved tensile strength properties, parafin waxes containingthe herein named small amounts of high molecular weight ethylene polymers possess improved The ethylene polymer in such blends does not segregate on rapid'cool- 'ing and does not produce any mottled effects in the cold wax.

The percentages referred to herein and in the "appended claims are weight percentages.

The wax compositions described herein can contain in addition to the high molecular weight ethylene polymers opacifiers, anti-oxidants or other modifying agent. Polymerized isobutylene can be added to the waxspolymeri'zed ethylene composition. i. l

While we have described our invention by reference to certain preferred embodiments thereof, the same is not limited thereto, except as defined by the appended claims.

We claim:

1. The method of preparing a high tensile strength petroleum wax composition containing an ethylene polymer having an average molecular weight of from about 5000 to about 25,000 comprising milling an ethylene polymer having an average molecular weight of about 5000 to about 25,000 with from about 5% to about 60% by weight of a petroleum wax .at a temperature of from about 220 F. to about 360 F. to obtain a homogeneous blend of said petroleum wax and said polymer and then dissolving a sufiicient amount of said blend in a petroleum wax at a temperature of from about 140 F. to about 250 F., to obtain a finalwax composition containing from about 0.001% to about 0.2% by weight of said polymer.

2. The method of claim 1 wherein the petroleum wax is a parafiin wax.

3. The method of preparing a wax composition containing an ethylene polymer having an average molecular weight of from about 5000 to about 25,000; comprising milling an ethylene polymer having an average molecular weight of from about 5000 to about 25,000 with from about 5% to about 60% by weight of a petroleum wax at a temperature of from about 220 F. to about 360 F. to obtain a homogeneous blend of said petroleum wax and said polymer, and then dissolving said blend in petroleum wax at a temperature of from about 140 F. to about 250 F. to obtain a complete solution of the ethylene polymer in the petroleum wax.

4. The method of preparing a wax composition containing an ethylene polymer having an average molecular weight of from about 5000 to about 25,000; comprising forming a homogeneous blend of an ethylene polymer having an average molecular weight of from about 5000 to about 25,000 with from about 5% to about 60% by weight of a petroleum wax at a temperature of from about 220 F. to about 360 F. and then dissolving said blend in petroleum wax at a temperature of from about 140 F. to about 250 F. to obtain a complete solution of the ethylene polymer in the petroleum wax.

5. A method for preparing an improved paraflin wax comprising melting together solid polymerized ethylene and parafiin wax in approximately equal quantities, mixing until hemogeneous, and subsequently adding thereto a quantity of molten paraffin wax such that the amount of polymerized ethylene in the combined wax and polymerized ethylene composition is from 0.001 to 7 per cent.

6. The method of preparing a wax composition containing an ethylene polymer having an average molecular weight of from about 10,000 to about 80,000 which comprises forming a homogeneous blend of an ethylene polymer having an average moleculer weight of from about 10,000 to about 80,000 with an approximately equal amount of a paraflin wax having a melting point between about F. and F. at a temperature above the melting point of said wax and then incorporating with said blend at a temperature above the melting point of said wax, an additional amount of said parafl'in wax to obtain a homogeneous wax composition.

7. The method of preparing a petroleum wax composition containing a solid ethylene polymer which comprises forming a homogeneous blend of a solid ethylene polymer with from about 5 to about 60 per cent by weight of a, petroleum wax at a temperature above the melting point of the wax and then incorporating with said blend at a temperature above the meltin point of said wax an additional amount of said wax to obtain a homogeneous wax composition.

8. The method of claim '7, wherein the petroleum wax is an amorphous petroleum wax.

9. The method of claim '7, wherein the petroleum wax is a paraffin wax.

JOHN R. BOWMAN. WILLIAM P. RIDENOUR. JUNE HOLLENBACK WI-IITTAKER.

References Cited in the file of this patent UNITED STATES PATENTS Name Date MacLaren Apr. 18, 1950 OTHER REFERENCES Number 

5. A METHOD FOR PREPARING AN IMPROVED PARAFFIN WAX COMPRISING MELTING TOGETHER SOLID POLYMERIZED ETHYLENE AND PARAFFIN WAX IN APPROXIMATELY EQUAL QUANTITIES, MIXING UNTIL HOMOGENEOUS, AND SUBSEQUENTLY ADDING THERETO A QUANTITY OF MOLTEN PARAFFIN WAX SUCH THAT THE AMOUNT OF POLYMERIZED ETHYLENE IN THE COMBINED WAX AND POLYMERIZED ETHYLENE COMPOSITION IS FROM 0.001 TO 7 PER CENT. 